In Patent Document 1, a resin molded article at the entire surface of which a hard skin layer with no pore is formed and inside which an expanded layer with a large number of pores is formed is obtained in such a manner that: a fiber-containing thermoplastic resin is injected and filled in a cavity of a mold, which includes a fixed die having a molding face in which a concave portion is formed and a movable die including a sliding die, with the mold closed; and in the process of solidifying the fiber-containing thermoplastic resin in the cavity, the sliding die in the movable die is withdrawn in the direction in which the capacity of the cavity is increased to expand the fiber-containing thermoplastic resin by elastic restoring force (a springback phenomenon) of the fiber compressed by resin pressure. This resin molded article, which includes the expanded layer, is lightweight. Patent Document 1: Japanese Patent Application Laid Open Publication No. 11-179751A (Pages 3 and 7 and FIG. 1)